The invention relates to directional boring machines that use an onboard sonde for controlling the direction of the bore.
Directional boring machines or trenchless drills for making holes through soil are well known. The directional borer generally includes a series of drill rods joined end to end to form a drill string. The drill string is pushed or pulled though the soil by means of a powerful device such as a hydraulic cylinder. A spade, bit or head having one or more angled faces configured for boring is disposed at the end of the drill string and may include an ejection nozzle for water or drilling mud to assist in boring.
In one known directional boring system, the drill bit is pushed through the soil without rotation in order to steer the tool by means of the angled face, which is typically a forwardly facing sloped surface. For rocky conditions, a row of teeth may be added to the drill bit and the bit operated in the manner described in Runquist et al. U.S. Pat. No. 5,778,991. Other toothed bits for directional boring through rock are shown in Cox U.S. Pat. No. 5,899,283, Skaggs U.S. Pat. No. 5,647,448 and Stephenson U.S. Pat. No. 5,799,740. Steering systems for use with these devices require keeping track of the angle of rotation of the sloped face of the bit and/or the teeth.
According to another known system, a transmitter or sonde mounted in a tubular housing is mounted behind and adjacent to the bit and sends a signal that indicates the angle of rotation of the bit. The sonde is mounted in a predetermined alignment relative to the steering portion of the bit. Since the sonde housing is generally made of steel, a series of longitudinal slots or windows are provided through the wall of the sonde housing to permit transmission of the signal. See generally Mercer U.S. Pat. No. 5,633,589, Hesse et al. U.S. Pat. No. 5,795,991, and Stangl et al. U.S. Pat. No. 4,907,658. Mounting of the sonde in its housing has been accomplished by end loading as illustrated by the foregoing patent to Stangl et al. or through a side opening which is closed by a door or cover during use, as illustrated in Lee et al. U.S. Pat. Nos. 5,148,880 and 5,253,721.
Prior attempts to use sondes in horizontal directional boring apparatus, particularly of the type for drilling consolidated rock formations, have proven less than ideal. Breakage of the sonde is to be avoided because sondes are expensive to replace. The sonde housing cover in side-loading sonde housings is prone to failure. The bolts used to secure the cover often loosen or break off as a result of the abrasion and stress applied to the sonde housing during boring, and the door or cover may work loose or collapse inwardly, crushing the sonde. A need remains for a more secure side-loading sonde housing which is nonetheless easy to open and close when necessary. The present invention addresses these concerns.
The present invention provides an improved apparatus for mounting an electronic device such as a sonde therein for use in directional drilling. Such an apparatus includes an elongated housing having projections at opposite ends of the housing for connecting the housing to other components of the boring machine and an elongated internal chamber configured to receive an electronic device therein. The chamber has an elongated access opening which extends along an exterior surface of the housing. A cover sized to close the access opening has a first hole extending therethrough. The housing includes a second hole which comes into alignment with the first hole when the cover is in position to close the access opening, and a third hole at least partially intersecting the second hole. When a pin having a head for holding down the cover is inserted in the first and second holes, a retainer such as a roll pin for engaging the pin may be inserted into the third hole in a manner effective to mechanically engage the pin so that the pin holds down the cover. According to preferred form of the invention, the pin preferably has an enlarged diameter head which seats against a step in the first hole to hold down the cover, and a groove that comes into alignment with an interior surface of the third hole when the pin is fully inserted so that the head of the pin engages the step. The retainer can then extend into the groove in the pin to prevent removal of the pin from the first and second holes. Preferably both the groove and the third hole have a circular profile so that an elongated, cylindrical retainer can fit therein.
According to a second aspect of the invention, a pin adapted for holding down a sonde housing cover comprises an elongated, generally cylindrical rod made of a rigid, hard material and having an enlarged diameter head. A concave groove is formed on the rod at a location spaced from the head along the length of the rod, and a button of a material harder than the rod material is centrally mounted on top of the head. The button is effective for inhibiting flattening of the head by hammering thereon during installation. The annular groove preferably has a circular profile in the lengthwise direction of the pin so that precise location of the pin relative to the retainer is not necessary.
According to a third aspect of the invention, a joint for coupling a pair of elongated members end to end includes a projection extending in a lengthwise direction from one end of one of the elongated members and a socket in an end of the other of the elongated members, which socket is sized to slidingly receive the projection. A first set of alignable transverse holes are formed in the projection and in a wall defining the socket, which openings are configured to receive a removable pin for mechanically interlocking the projection in the socket. A second set of alignable transverse holes formed in the projection and in a wall defining the socket are configured to receive a removable retainer for mechanically interlocking the pin in the first set of alignable transverse holes. In a manner analogous to the first aspect of the invention, the second set of alignable transverse holes at least partially intersects the first set of alignable transverse holes, whereby when a pin is inserted in the first set of holes, a retainer for engaging the pin may be inserted in the second set of holes in a manner effective to engage the pin so that the pin remains in the first set of alignable transverse holes. These and other aspects of the invention are described in detail below.